Hi Dear, Welcome to HCM, Understanding your concern . As per your query persistent bad breath and metallic taste in mouth is mainly because of Dehydration or oral cavity which occur due to infection n oral cavity like gingivitis or periodontitis .Sometimes dental abscess or sinus formation can also cause such kind od bad odor and metallic taste in mouth .I would suggest you to maintain proper oral hygiene , Brush and floss twice a days , do warm saline rinses thrice and consult dentist for proper diagnosis . Doctor will examine physically to tule out conditions like acid reflux . Dentist may perform oral prophylaxis and prescribe antibiotics like metronidazole . If there is any any abscess the doctor may drain abscess or perform root canal in that tooth . As of now you can chew sugar free chewing gum and tart candies as it help in stimulating saliva flow. Gargle with Biotene mouthwash. Drink plenty of water.. Hope your concern has been resolved. Get Well Soon. Best Wishes, Dr. Harry